There are a number of procedures and applications that involve the formation of a temporary seal or plug while other steps or processes are performed, where the seal or plug must be later removed. Often such seals or plugs are provided to temporarily block a flow pathway or inhibit the movement of fluids or other materials, such as flowable particulates, in a particular direction for a short period of time, when later movement or flow is desirable.
The recovery of hydrocarbons from subterranean formations often involves applications and/or procedures employing coatings or plugs. In instances where operations must be conducted at remote locations, namely deep within the earth, equipment and materials can only be manipulated at a distance. One such operation concerns perforating and/or well completion operations incorporating filter cakes and the like as temporary coatings.
Generally, perforating a well involves a special gun that shoots several relatively small holes in the casing. The holes are formed in the side of the casing opposite the producing zone. These perforations, or communication tunnels, pierce the casing or liner and the cement around the casing or liner. The perforations go through the casing and the cement and a short distance into the producing formation. Formations fluids, which include oil and gas, flow through these perforations and into the well.
The most common perforating gun uses shaped charges, similar to those used in armor-piercing shells. A high-speed, high-pressure jet penetrates the steel casing, the cement, and the formation next to the cement. Other perforating methods include bullet perforating, abrasive jetting, or high-pressure fluid jetting.
The characteristics and placement of the communication tunnels can have significant influence on the productivity of the well. Technology has been developed which eliminates the need for perforating guns and enables significantly more controlled perforation through the use of fluid conduits installed within casings. These fluid conduits may be extended out from the casing to contact a formation wall, thereby forming “perforations” at desired locations along the length of the casing. Temporary plugs in the conduits form fluid barriers, and the conduits are pushed out from the casing via fluid pressure. The plugs may be made of a porous filter structure on which a degradable barrier material is coated. After the fluid conduits are extended, the degradable material may be removed, thereby allowing the flow of fluids through the filter structure. This technology, known as TELEPERF™ from Baker Hughes Inc, is described in more detail in U.S. Pat. Nos. 7,527,103 and 7,461,699, each incorporated by reference herein its entirety.
In some instances, it may be necessary or desirable to fracture a formation to enable or promote the flow of fluids therethrough. For example, in low-permeability reservoirs, it may be beneficial to fracture the well formation and inject proppants into the fractures to stimulate the flow of fluids (such as oil, gas, water, and the like) through the formation. When hydraulic fracturing is performed, the viscous fracturing fluids mixed with proppant are flowed into the formation through the casing and associated perforations. However, filters in the above-described TELEPERF™ devices may obstruct or impede the high-viscosity fluids and proppants utilized in hydraulic fracturing from entering the formation.
Accordingly, hydraulic fracturing may be accomplished in TELEPERF™ devices by temporarily plugging the telescoping conduits to inhibit the flow of fluid therethrough. Hydraulic pressure telescopes the flow conduits outward, and the temporary plugs may then be removed from the flow conduits via an acidic solution. High-viscosity fluids and proppants may then be injected to fracture the subterranean reservoir. This technology, known as TELEFRAC™ from Baker Hughes Inc, is described in more detail in U.S. patent application Ser. No. 12/723,983, which is herein incorporated by reference its entirety.
Although the TELEFRAC™ method described above enables proppant fracturing through the TELEPERF™ tunnels, the system does not provide for a filter structure through which the formation fluids may be returned to the well surface. It may be desirable to filter the formation fluids in order to control proppant flow back into the wellbore. Ensuring that the proppant remains in the fracture will increase the fracture integrity in the near wellbore region and maintain higher productivity that results from well fracturing.